I. Field of the Invention
This invention relates generally to microwave transmission apparatus and more particularly to apparatus used to transition from coaxial transmission lines to waveguides. In many applications it is desirable to maintain a positive gas pressure in the waveguide. The present invention is directed toward such applications.
II. Description of the Prior Art
Microwave systems are frequently designed to employ pressurized waveguides which function to keep the system clean and dry thereby avoiding problems associated with contaminants and moisture condensation. Additionally, waveguide pressurization can function to increase the power carrying capability of the waveguide. Pressurized waveguide to coaxial line transitions are commonly used on the secondary arms of waveguide couplers which monitor power in a system. When confronted with the design requirement for a pressurized transition, workers in the prior art have been able to select from a variety of alternative solutions, none of which have been entirely satisfactory. For example, hermetically sealed waveguide to coaxial line adaptors have long been available at a very large cost increment over similar unsealed adaptors which are not suitable for use in pressurized systems. Alternatively, some workers have attempted to modify commercialy available unsealed adaptors by sealing those portions where leakage may occur with an epoxy type sealant. If only a small amount of such sealant is used, it may have a tendency to crack and leak following repeated environmental cycling. If an excessive amount of such an epoxy sealant is used, it can cause an electrical mismatch or high VSWR.